2.4.1. Direct Media Connection (DMC) 
The HG 35xx gateways support Direct Media Connections (DMC).
More detailed information on Direct Media Connections
The HG 35xx gateways support Direct Media Connections (DMC also referred
to as peer-to-peer) between two IP phones or an IP phone and an IP board
like another HG 3500 or HG 3575. Payload between two DMC endpoints (DMC
endpoints = IP phone, HG 3500/3575) is switched entirely in the IP network
without involvement or the TDM switching matrix. This ensures highest
quality voice and minimal delays because only a single hop (TDM to IP
to TDM conversion) is required.
IMPORTANT:
Note that invoking any feature that results in
a multi party call (more than 2 parties) will route the payload through
all gateways in the payload path. This may result in undesirable delays
in certain scenarios (see Section 2.5.6,
“DMC Considerations” for more details).
Bandwidth is required for the master connection in addition to the
DMC connection. The required bandwidth for the master connection can
virtually be eliminated by using VAD for the IP clients. In case VAD
cannot be enabled then twice the bandwidth is required.
For more information on DMC and bandwidth please refer to Section 2.5.6,
“DMC Considerations”.